Bovine papillomavirus (BPV) type 1 and type 2 DNA sequences have been detected in numerous naturally occurring equine connective tissue tumors and cell lines established from virus-induced equine and bovine fibromas. Most of the sequences appear as superhelical forms with no evidence of integration into the host genome. To delineate the function of the BPV genome in these tumor cells, virus-specific RNA transcripts will be positioned on the restriction endonuclease cleavage maps of the virus genomes. Mouse cells transformed by BPV and other papillomaviruses will be analyzed for integrated viral DNA sequences and synthesis of virus mRNA. Conserved polynucleotide sequences have been shown to exist among the genomes of papillomaviruses of human, rabbit and bovine origin. Studies are underway to further examine the extent of this evolutionary relateness among these viruses. To obtain sufficient quantities of virus DNA for study, DNAs from human, dog, ox, horse, goat and deer papillomaviruses are being molecularly cloned. Additionally, various tumors are being examined for conserved papillomavirus polynucleotide sequences employing intact virus DNA and subgenomic fragments as probes.